<template>
  <div>Son</div>
  <p>{{ num }}</p>
  <button @click="$emit('update:num', num + 1)">更新</button>
</template>

<script lang="ts">
export default {
  name: "Son",
  props: {
    num: {
      type: Number,
      required: true,
    },
  },
  emits: ["update:num"],
};
</script>
